In general, implantable medical devices (IMDs) provide in situ therapy delivery, such as cardiac resynchronization, defibrillation, neural stimulation and drug delivery, and physiological monitoring and data collection. Once implanted, IMDs function autonomously by relying on preprogrammed operation and control over therapeutic and monitoring functions. As necessary, IMDs can be interfaced to external devices, such as programmers, repeaters and similar devices, which can program, troubleshoot, recharge and exchange parametric and physiological data, typically through induction or similar forms of near-field telemetry.
Typically, therapy delivery and physiological data monitoring and collection are performed in conjunction with a closed-feedback loop that includes one or more sensors provided with each IMD. For example, sensors included on the distal end of electrode leads of an implantable cardiac defibrillator (ICD) can monitor intracardiac electrical activity preceding and subsequent to therapy delivery. However, the feedback is limited only to the activity sensed within the intracardiac area immediate to each sensor and such feedback may be insufficient to determine whether the therapy was effective. Moreover, additional physiological parameters that might be helpful in ascertaining therapy efficacy, such as blood pressure, chemistry or body temperature, remain unavailable to the ICD due to the limited functionality provided by the local electrode lead sensors.
Certain IMDs can be supplemented with additional implantable sensors to monitor physiological data in other locations of a patient's body, such as described in Medtronic, Inc., “Research Presented at ADA Annual Meeting Demonstrates Accuracy and Feasibility of Artificial Pancreas Components,” News Release, http://www.medtronic.com/newsroom/news—20020617b.html (Jul. 17, 2002), the disclosure of which is incorporated by reference. Currently, such sensors can interface to an IMD through a wired interconnection or can operate autonomously. Neither approach provides a satisfactory solution. Wired interconnections are highly invasive, potentially requiring an intra-body tunnel to channel interconnect wires. Such intra-body tunneling exposes the patient to possible adverse side effects, including injury to internal tissue and organs, infection and discomfort. In addition, coordinating communications with the IMD becomes increasingly complex with the addition of each additional wired sensor, which also requires an interconnection interface and dedicated set of interconnect wires.
Autonomous operation avoids the side effects of wired interconnections and instead relies upon the external download of stored physiological data. External data download can be critical, as most implantable sensors have limited on-board storage, often only available for storing episodic data observed over a recent time period. Externally downloaded physiological data, though, can only be made available to the IMD indirectly by relay through an external device. As a result, the downloaded physiological data is untimely and of less use than real time physiological data received directly from each implantable sensor.
For example, U.S. Pat. No. 7,024,248, issued on Apr. 4, 2006, and U.S. Pat. No. 7,273,457, issued on Sep. 25, 2007, both describe an implantable sensor interfaceable via an external acoustic transducer. The sensor functions autonomously to monitor pressure or physiological parameters. The acoustic transducer transmits acoustic signals into a patient's body to interface with the implantable sensor, which downloads pressure measures recorded by the sensor. Each individual sensor is a stand-alone device and is not configurable into a network arrangement allowing direct communication between implantable sensors and IMDs.
Therefore, there is a need for an approach to providing non-wired interconnectivity between a plurality of implantable devices, including one or more IMDs and one or more implantable modules and preferably supporting configuration as a master-to-slave or peer-to-peer network configuration.
There is a further need for an approach to providing a network communications protocol facilitating the data exchange between wireless modules within an intra-body digital data communications network, preferably providing both physical and application layers to support a plurality of application types.
There is a further need for an approach to providing flexible external interfaces between a plurality of external devices and implantable modules configured into an intra-body digital data communications network. Preferably, such an approach would support communication with a programmer, repeater or special purpose device, such as a recharger, through high efficiency interfaces.